This has been a mystery which has baffled a lot of people.Windows 7 which sprung into limelight with its stunning looks & other state of the Art features also came with a few major bugs which are yet to be fixed by Microsoft.A few issues involves the memory leaks,sudden disappearance of Administrator tools N more.But none of them can be formidable than the issue where the Hard disk spaces keeps vanishing without any trace.By Googling for the fixes,I came across a few potential reasons behind this of which the major suspects comprised of:

System Restore

Winsxs Folder

Pagefile.sys

Hibernate.sys

But have you ever heard of a folder called PC DM files?Probably no.I was also a victim of the perplexing disk issue and I had written a blog on that,which can be found here.Although when i implemented the methods,I was able to recover more than 6-7 Gb of my Hard disk & I felt relieved that the issue was fixed for once & for all.But to my dismay,the hard disk space was disappearing right in front of my eyes.Everytime I restarted my laptop,I was loosing 300+ Mb and I was not even installing or downloading anything.I kept moving files from C drive(Windows drive)to the other ones.But the issue persisted & I thought that there was no other option but to re-install my Os as the issue seems anything but fixed.

Then my brother Vimal me recommended to use a software called WinDirStat:A freeware which can show the Disk utilization & gives a very good graphical interpretation of the files & folders and its corresponding space allocation.You can grab it from here.Installed it reluctantly and then decided to scan the disks for one last time.Then something got my attention.I found that one particular folder was occupying 19.4Gb of the disk space and it was not visible in the explorer view(Show hidden files & folders was enabled).It's folder name was PC DM files & within it contained a folder,which had the name of my Login screen(Home in my case).Inside the folder it was all backup files.There were so many of them!!The list was never ending and I decided to Shift+delete it & when I did I got back my 19Gb space and now my issue has been fixed.No thanks to Microsoft though.You need to delete the file via the WinDirStat as its not visible in the explorer view.You can have a detailed look here:

I had uploaded this pic after I deleted the bulk folder.The folder will reappear(Its Home in my case,but you can delete it safely).I guess I may have resolved the issue once and for all.Incase you found this post useful please do try to comment.